Estimation of Optimum Blend Ratios of Biodiesel for Diesel Engine
4.3 Results and Discussion
4.3.2 Engine Performance Analysis
(a) (b)
Figure 4.8: Blending effect on cetane number: (a) COME-diesel blends (b) POME-diesel blends.
Table 4.4: Testing properties of blended fuel: (a) COME biodiesel/diesel blends; (b) POME biodiesel/diesel blends.
Fuel property Blend fuel code
Blended biodiesel standards(Handling and Guide,
2009; Silitonga et al., 2013) (a) COME biodiesel/diesel blends
CBD0 CBD10 CBD20 CBD30 CBD40 CBD50 CBD60 CBD70 CBD80 CBD90 CBD100 ASTM D7467 BIS
Kinematic viscosity at 40◦C 3.23 4.01 5.18 9.58 12.18 14.01 15.81 16.67 18.06 19.73 21.91 1.9−4.1 2.0−4.62
Density at 27◦C 838 842 851 857 864 876 889 906 914 931 943 820-860 820−860
Cloud point (CP),°C -6 -4 -2 0 3 5 6 8 11 13 14 - -
Pour point (PP), °C -8 -5 -4 -2 1 2 4 6 8 10 12 - 3 max. winter
Flash point, °C 62 64 65 68 70 77 88 92 105 124 155 min. 52 min. 35
Fire point, °C 66 67 69 73 76 83 90 98 110 131 168 - -
Calorific value, MJ/kg 44.69 44.874 44.817 44.236 43.681 42.393 41.378 40.835 40.366 39.878 38.412 - -
Cetane number 51 51.09 51.12 51.15 51.22 51.36 51.74 52.06 52.23 52.64 52.83 min. 40 -
(b) POME biodiesel/diesel blends
PBD0 PBD10 PBD20 PBD30 PBD40 PBD50 PBD60 PBD70 PBD80 PBD90 PBD100 ASTM D7467 BIS
Kinematic viscosity at 40◦C 3.23 3.51 3.98 4.58 5.18 6.01 7.21 7.67 8.06 8.53 8.71 1.9−4.1 2.0−4.1
Density at 27◦C 838 841 843 862 872 889 901 912 928 939 946 820-860 820−860
Cloud point (CP),°C -6 -5 -3 0 1 2 3 5 7 9 11 - -
Pour point (PP), °C -8 -6 -5 -3 -1 1 2 3 5 7 8 - max. 3
Flash point, °C 62 75 89 135 172 194 212 228 245 260 265 min. 52 min. 35
Fire point, °C 71 78 93 146 185 199 227 232 257 268 272 - -
Calorific value, MJ/kg 44.69 44.982 44.911 44.493 43.715 42.626 41.723 41.225 40.889 40.278 39.794 - -
Cetane number 51 51.29 51.66 52.42 54.02 55.76 57.18 58.81 60.03 60.54 60.84 min. 40 -
Table 4.5: Comparison of engine performance and emission parameters of biodiesel/diesel blending testing.
Fuel property COME-Diesel blend fuels POME-Diesel blend fuels
CBD0 CBD10 CBD20 CBD30 CBD40 PBD0 PBD10 PBD20 PBD30 PBD40
Brake power, kW 3.5823 3.37019 3.31657 3.22981 3.10893 3.5823 3.4291 3.3867 3.3278 3.2956
BSFC, kg/kW.hr 0.26857 0.29658 0.37276 0.41889 0.45752 0.26857 0.28134 0.35356 0.38876 0.42662 BTHE, % 29.70685 26.54991 20.1432 18.40204 16.63701 29.70685 28.44672 22.67183 19.32171 18.03504 CO Emission, % 0.396875 0.36594 0.32531 0.28158 0.16865 0.39687 0.33924 0.27531 0.22158 0.12865
HC Emission, ppm 98 94 82 67 52 98 83 69 57 45
NOx Emission, ppm 398 404 414 426 443 398 443 462 489 521
4.3.2.1 Effect of Blending on Brake Power (bp)
Figure 4.9 shows the engine brake power for different blends of fuel at full engine load. It can be seen that brake power decreased marginally with increasing percentage fraction of biodiesel in blends. Figure 4.9(a) illustrates the brake power of COME biodiesel diesel blends of fuel (CBD0, CBD10, CBD20, CBD30 and CBD40) at full engine load. As a comparison, the brake power achieved for diesel fuel (CBD0) was about 5.92, 7.42, 9.84 and 13.21 % higher than that of the blended fuel CBD10, CBD20, CBD30 and CBD40 respectively, at the same engine conditions.
Similarly, for POME biodiesel diesel blends of fuel of PBD10, PBD20, PBD30 and PBD40, the brake power was found lower by 4.27, 5.46, 7.10 and 8.0%, respectively as compared to diesel (PBD0) as shown in Figure 4.9(b). The reason for the lower brake power of biodiesels compared to diesel can be attributed to their lower calorific values and higher viscosities. Both the calorific value and viscosity have an effect on the combustion. Additionally, uneven combustion characteristics of biodiesel fuel decreased the engine brake power (Muralidharan et al., 2011).
Furthermore, it is seen that the average brake power reduction for CBD10−CBD30 in comparison to CBD0 fuel is 5−9%, whereas for PBD10−PBD30, it is 4−8%, respectively.
(a) (b)
Figure 4.9: Effect of blending on brake power (BP): (a) COME-diesel blends, (b) POME-diesel blends.
4.3.2.2 Effect of Blending on Brake Specific Fuel Consumption (BSFC)
The BSFC is defined as the fuel flow rate per unit power output. It can be considered as a measureof the engine efficiency in using the supplied fuel to produce work. The BSFC is one of the most important parameters to evaluate engine performance with various fuels and it can be calculated based on the engine brake power and fuel mass flow rate for each speed. The BSFC of diesel engine depends on the relationship among volumetric fuel injection system, fuel density, viscosity and lower heating value (Qi et al., 2010). Figure 4.10(a−−−−b) shows the variation of BSFC for all samples at full load engine running conditions. It is seen that the BSFC for biodiesel-blended fuels is higher compared to diesel. The minimum BSFC kept for diesel, which increased with increasing biodiesel ratios in the blended fuel. The results for BSFC shown in Figure 4.10(a), proved that there is a significant difference among the fuels. As a comparison, the BSFC for diesel fuel (CBD0) was about 10.43 %, 38.79 %, 55.97 % and 70.35 % lower than that of the blended fuel CBD10, CBD20, CBD30 and CBD40, respectively, whereas, the BSFC for diesel fuel(PBD0) was about 4.75 %, 31.64 %, 44.75 % and 58.85 % lower than that of the blended fuel PBD10, PBD20, PBD30 and PBD40, respectively (Figure 4.10-b). This difference in BSFC with diesel and blended fuel is due to the high density value of biodiesel blended fuel compared to mineral diesel. The average BSFC for CBD0, CBD10, and CBD20 is 0.26857 kg/kW.hr, 0.29658 kg/kW.hr, and 0.37276 kg/kW.hr, respectively. while, for PBD0, PBD10 and PBD20 of was 0.26857 kg/kW.hr, 0.28134 kg/kW.hr, and 0.35356 kg/kW.hr, respectively. The reason for the higher BSFC of biodiesels can be attributed to the combined effects of the relative fuel density, viscosity and heating value of the blends (Chauhan et al., 2012). Biodiesel fuel is delivered into the engine on a volumetric basis per stroke; thus, larger quantities of biodiesel are fed into the engine. Therefore, to produce the same power, more biodiesel fuel is needed because biodiesel has a lower calorific value compared to diesel fuel (Lin et al., 2009; Tsolakis et al., 2007). Among the blend CBD10 and PBD10 are lowest at full engine load which is normally the optimal for any diesel engine. Hence, for BSFC point of view CBD10 and PBD10 may be advantages. This is because of the lower fuel flow rate due to high density of the blends. Higher proportion of castor and palm oil in the blends increase the viscosity which in turn increased the BSFC due to poor atomization of fuel.
4.3.2.3 Effect of Blending on Brake Thermal Efficiency (BTHE)
The BTHE is the ratio of the thermal power available in the fuel to the power that the engine delivers to the crankshaft. It is an indicator of the operation with the test fuel. This parameter is a better evaluation than fuel consumption for the performance of different fuels, besides heating value. Since thermal efficiency is normalized to the fuel heating value, it depends heavily on the manner in which the energy is converted. The BTHE is slightly higher with increasing biodiesel ratios in the blended fuel as shown in Figure 4.11(a−−−b). Accordingly, the average reductions of − BTHE of the blended fuel CBD10, CBD20 and CBD30 and CBD40 are 11 %, 32%, 38 %, and 44
% respectively, which is lower than that of the mineral diesel (CBD0) under the same engine conditions. Similarly, for PBD10, PBD20, PBD30 and PBD40 were decreased by 4.24%, 23.96%, 34.96% and 39.29% with respect to diesel (PBD0). This difference may be attributed to the high kinematic viscosity of the blended fuel compared to mineral diesel, which affects the fuel vaporization and combustion process. Thus, the efficiency of CBD10 and PBD10 are close to diesel. This is due to the more amount of diesel presence in blended fuel. The amount of diesel is decreased in the CBD20, PBD20, CBD30, PBD30, CBD40 and PBD40 blends, respectively, which is recorded loss in efficiency. In maximum load, for CBD10 and PBD10 blends the efficiency are 26.6% and 28 % and for diesel is 29.7%.
(a) (b)
Figure 4.10: Effect of blending on BSFC: (a) COME-diesel blends, (b) POME-diesel blends.
(a)
(b)
Figure 4.11: Effect of blending on BTHE: (a) COME-diesel blends, (b) POME-diesel blends.